Is it possible to change Y-axes shortcut?
It's not so hard as looks like, you can set it in "User Preferences" ("Input" tab):


You need to find the drop-down list "Transform Modal Map" (it is near end of the list)
There isn't Y-axis in it, but you can add and setup it by pressing
"Add new" button. 
Next, select "Orientation Y axis" and setup shortcut





  Hey, what about "Shift-Y" which stands for "transform along every axes
  BUT Y"?


For "Shift-Y" analog use Orientation Y plane. This is a final setup: